Sensitive relay



M y 1951 F. G; BOUCHER 2,553,354

SENSITIVE RELAY Filed April 23, 1948 Patented May 15, 1951 UNITED STATES PATENT OFFICE 2,553,354 s'ENSiT'IVE RELAY Frank G. Boucher, Tulsa, Okla, 'assig'nor to Standard Oil Development company, a comic-- ration of- Delaware Application April 23, 1948, serial No. 22,741

I 4 Claims.

This invention relates to an improved type of a sensitive relay. In particular the invention relates to a novel relay construction permitting positive relay action in response to exceedingly small currents.

The increasing use of electronic control and analytical instruments in many industries has been accompanied by the need of improved electrical components of the circuits used. Thus at the present time, for example, presently known relays are not suitable in some applications. As is well known, a relay is an apparatus containing two electrical circuits with means responsive to a comparatively small change of voltage or current in one of the circuits to produce a comparatively large change of voltage or current in the other circuit. Relays generally employ an electromagnet energized by the less powerful circuit to open or close contacts of the circuit carrying the more powerful energy. When it is necessary to activate a relay with extremely small currents it is customary to employ a vacuum tube. While sensitive relays have been proposed, designed to Work at relatively low currents, no relay presently available gives positive action for currents as low as microamperes. t is, therefore, the principal purpose of this invention to provide an innproved type of relay which will positively respond to the extremely small currents of the magnitude indicated, without the necessity of employing, a vacuum tube for amplification.

Furthermore, in conventional relays, the relays are characterized by requiring a continuous flow of a substantial current through the less powerful circuit to maintain positive closure of the contacts of the more powerful circuit. It is, therefore, a further object of this invention to provide a relay which will maintain positive closure of the high power circuit while requiring no more than the minimum sensitizing current to flow in the low power circuit.

In accordance with the present invention, a sensitive relay is connected with a polarized relay and auxiliary electromagnetic elements in a novel manner. The electromagnetic elements referred to are so connected as to positively pull the sensitive relay arm against the relay contacts when the sensitive relay is activated, the closure of the sensitive relay operating the polarized relay to control circuits which may be used for the higher power circuits. Thus the sensitive relay in the apparatus of the invention, aided by auxiliary electromagnets, is only utilized to respond to an extremely low current, and is operative to control a polarized relay through which higher our-- rents may be drawn. The apparatus of this invention will be better understood by reference to the accompanying drawing wherein is shown diagrammatically an embodiment of this invention.

Referring to the drawing, the numeral I generally indicates a sensitive relay comprising the elements 2, 4, 5 and 6. With the exception of the tip of the relay arm 4, this sensitive relay may be of conventional construction. For example, a suitable relay is the Weston 534 sensitive relay. It is to be understood, however, that any suitable sensitive relay may be employed. As diagrammatically shown, the relay comprises a field magnet 2, a coil 5 and a relay arm A. In response to suitable currents in coil 5, the relay arm 4 is moved to right or left, dependent upon the current in coil 5. Sensitive relays of the type indicated generally are constructed in the nature of an ammeter, the relay arm corresponding to the needle oi the ammeter.

In accordance with this invention the tip of the relay arm 4 is modified as diagrammatically illustrated. Positioned on the end of the relay arm 4 is a soft iron slug 6. Contacts 3 and l connect ing to arm 4 are brought out from the arm so as to sandwich the iron slug. As will be seen, electromagnets will attract the iron slug causing contact 3 or 1 of arm 4 to positively close auxiliary circuits connected with polarized relay 8.

Again polarized relay 8 may be of conventional construction. This type of relay, as the name implies, is characterized by movement of the relay arm When activated, to either of two positions and maintenance of the relay arm in the particular position until movement of the arm is again activated. Thus in the relay 8 illustrated, flow of current through coil 9 of the relay will cause relay arm H] to move to the left against contact II and will maintain the relay arm against this contact. Similarly, flow of current through coil [2 of the relay will cause the relay arm to move to the right against contact [3 and will also hold the relay arm against this contact. Thus relay arm I0 will always be either in the left or in the right position. Positioned on each side of the iron slug 8, are electromagnets l4 and I5. The armatures of the electromagnets are so positioned that they will be contacted on movement of the relay arm 4, to right or left. As will be developed, the function of these electromagnets is to attract the iron slug 6 to right or left, as the associated circuits are operated. The armature of electromagnet I4 is connected to lead 16 which is connected to one side of coil 9 of the polarized relay, generally identified by the number 8 on the drawing. As stated, this polarized relay may be of conventional construction. For example, a suitable type of polarized relay is the American Automatic Electric series P. H. D. polarized relay. The other side of coil 9 of the polarized relay is connected to the relay arm I and also to one side of the other coil I2 of the relay, which connection serves as a junction point for lead I'I. Lead I1 is connected to a battery I8, and the other side of this battery is connected to conductors I9 and 2I. Lead I9 is connected to the movable arm 4 of the sensitive relay. This connection is preferably made by spiraling a light lead as indicated by the number 20, so that movement of the arm 4 will not be impeded by the connection of the lead. Lead 2I is connected to a portion of the circuit to be hereinafter described. Similarly, the armature of electromagnet I is connected to conductor 22, which is connected to coil I2 of the polarized relay 8.

As described heretofore, on activation of the sensitive relay I by the flow of a control current through coil 5, the relay arm 4 will be moved either to the right or to the left. Movement of the arm to the right will close an electrical circuit running from the battery I8 through lead I 9, arm 4, contact I, the armature of electromagnet I5, lead 22, and coil I2 of the polarized relay. This will cause the arm is of the polarized relay to similarly move to the right against contact I3 and to close other contacts, which will be arranged in a load circuit. For the purposes of simplicity these loading contacts of the relay are not illustrated separately but are represented by contacts II and I3. Thus, when arm I9 engages contact I3 an external circuit through conductors 30 and 32 will be established and when arm I0 engages contact I I an external circuit through conductors 30 and 3| will be set up. Similarly, when activating current is passed through coil 5 in the opposite direction, the arm 4 will be moved to the left to contact the armature of electromagnet I4, closing the electrical circuit from the battery I8, through coil 9 of the polarized relay.

As stated, the electromagnets I4 and I5 are operative to aid the movement of relay arm A. This is accomplished by connecting one side of the electromagnet I4 to lead 23 which is connected to the contact I3 of the polarized relay. The other side of the coil of electromagnet I4 is connected to the junction point 24 of conductor 2| of the battery I8. Similarly one side of the coil of electromagnet I5 is connected to the contact II of the polarized relay, through conductor 25, while the other side of this coil is connected to junction point 24, connecting to lead 2| and the battery I8.

By nature of the circuits described, when the arm 4 of the sensitive relay is moved either to the right or to the left, the arm I0 of the polarized relay will similarly be moved to the right or to the left. For example, if arm 4 is moved to the right, a circuit will be established through the battery I8 and the coil 12 causing the arm In of the relay 8 to move to the right against contact I3. On connection of the arm I9 and the contact I3, a circuit will then be completed from the battery I8, lead I'I, arm I0, contact I3, lead 23, electromagnet I4 and lead 2I. This will cause a current to flow in the coil of electromagnet I4 setting up an electromagnetic force attracting the iron slug 6 of the arm 4. The coil used, and the battery voltage supplied is so chosen, however, that insufiicient pull will be exerted on the slug 6 to pull the arm 4 away from its position against the armature of electromagnet I5. However, sufficient pull is exerted by the electromagnet I4 so that if the arm 4 is caused to move somewhat to the left, the slug 6, will be pulled forcibly toward the electromagnet I4. Contact of the relay arm 4, with the armature of electromagnet I4, will then close the circuits formerly described, through the coil 9 of the polarized relay and through the electromagnet I5, thereby activating the system for a response in the opposite direction.

As described, therefore, the apparatus of this invention comprises a combination of a sensitive relay with a polarized relay. The circuits combining these relays are so arranged that on closure of the sensitive relay, the polarized relay is caused to close load circuits and at the same time closes a circuit through an electromagnet adapted to pull the sensitive arm of the relay to the other of its two positions. By virtue of this arrangement any current in the coil of the sensitive relay, sufiicient to move the arm of the relay away from one of the contacts, will enable the electromagnets adjacent to the arm to positively close the circuits through the relay arm.

It will be apparent from the description of the apparatus given, that the apparatus comprises a means for securing a positive movement of the relay arm of a sensitive relay, making it possible to use exceedingly small currents to activate the sensitive relay. As an example of the efficiency of this apparatus, a typical construction embodying the principles taught herein enabled positive action of the relay circuit with currents as low as 29 microamperes. The advantages of the apparatus of this invention will therefore be apparent.

Having now fully described this invention, what is claimed is:

1. An improved relay apparatus comprising a sensitive relay having a relay arm adapted to be thrown to a first contact position upon being energized by a small current flowing through said relay in one direction and to a second contact position upon being energized by a small amount of current flowing through said relay in the opposite direction, electrical contacts in the said relay associated with each of said contact positions, a polarized relay provided with a first activation means adapted to throw said polarized relay to a first contact position and with a second activation means adapted to throw said polarized relay to a second contact position, means connecting said first activation means with the electrical contact associated with said first contact position of said sensitive relay, means connecting said second activation means with the electrical contact associated with said second contact position of said sensitive relay, a first electromagnetic means adapted to exert a small pull on the arm of said sensitive relay toward its first contact position, a second electromagnetic means adapted to exert a small pull on the arm of said sensitive relay toward its second contact position, means for energizing said first electromagnetic means when said polarized relay is in its second contact position, and means for energizing said second electromagnetic means when said polarized relay is its first contact position.

2. Improved relay apparatus according to claim 5 l in which a mass of iron is provided on the movable arm of the sensitive relay adjacent said first and second electromagnetic means to aid the action of said first and second electromagnetic means.

3. An improved relay apparatus comprising in combination a sensitive relay of the ammeter type provided With a field magnet, a movable relay arm at least a portion of which is magnetic, at least two contact points, and a coil adjacent said relay arm adapted to move said arm in one of two directions so as to engage one of said two contact points, dependent upon the direction of current flow through said coil, electromagnets disposed adjacent each of said contact points, a polarized relay provided with a first coil adapted to throw said polarized relay to a first contact position and with a second coil adapted to throw said polarized relay to a second contact position, electrical contacts in said polarized relay associated with each of said contact positions, an electrical circuit connecting said first polarized relay coil with the first of said two sensitive relay contact points, an electrical circuit connecting said second polarized relay coil with the second of said relay contact points, an electrical circuit connecting the contact points associated with the first contact position of said polarized relay with the electromagnet adjacent the second of said sensitive relay contact points and an electrical circuit connecting the contact points associated with the second contact position of said polarized relay with the electromagnet adjacent the first of said sensitive relay contact points.

4. Improved relay apparatus according to claim 3 in which the movable end of said sensitive relay arm engaging said contact points is provided with a small mass of soft iron.

FRANK G. BOUCHER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,780,676 Hough Nov. 4, 1930 2,200,128 West May 7, 1940 2,444,619 Smith July 6, 1948 

